THE COMPOUND MICROSCOPE 



pcHtant point we must notice before we leave the 

 diagram. We have mentioned several times that 

 the image formed by BB is erect and so it is, but 

 it is an erect image of an already inverted image, 

 so that the final image of CD, as seen by the eye E 

 is inverted. The fact that objects viewed through 

 the microscope appear upside down is puzzling at 

 fiist. To all intents our two double convex lenses 

 Ttpteaent a ctMnpound microscope; actually, they 

 sfaoald be fixed at either end of a tube, blackened 

 cm the inside. The lens AA, neaiest to the object, 

 wovdd then be known as tfae objective and the lens 

 BB neaiest to the observer's eye would be known 

 Bs the oeolar or, more conmionly the eyepiece. There 

 aie, of course, very many refinements, designed to 

 make the instrament capable of peKforming the most 

 aocnrate wc»k, and needless to say these simple 

 knses woold neither give very great magnification 

 nor any ciear images. Let ns describe a more refined 

 oompoond micfoaeope than the one we constructed 

 in oar darkened room. The optical parts, that is to 

 say the lenses, aie the most inqmrtant parts of every 

 microseope, upoa thdr qualities depend the degree 

 ci eflkacncy ei fbe instramoit; the metal portions, 

 known o^leetivdly tm the w^aad^ cu nU ib nte to the 

 easier, smoothor wofking of the microsoope. 



The stand most daim our attrition first. Tfe 

 base of tiie iusUum cBt, called tiie loot, is nsoally 

 other three-legged or hone-shoe shaped; whatever 

 its form it dioold be heavy, ix onfy thns can the 

 micEoscope be steady, nod steadiness is essential in 



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